package sort;

import java.util.Arrays;

/**
 * \* User: MeiZhongHao
 * \* Date: 2019-04-09
 * \* Time: 17:33
 * \* Description:
 * \
 */
public class MergeSort {


    public static int[] mergeSort(int[] array) {
        if (array.length < 2) {
            return array;
        }
        int mid = array.length / 2;
        int[] left = Arrays.copyOfRange(array, 0, mid);
        int[] right = Arrays.copyOfRange(array, mid, array.length);
        return merge(mergeSort(left), mergeSort(right));
    }

    private static int[] merge(int[] left, int[] right) {
        int[] result = new int[left.length + right.length];
        for (int index = 0, i = 0, j = 0; index < result.length; index++) {
            // left、right已排好序了
            if (i >= left.length) {
                result[index] = right[j++];
            } else if (j >= right.length) {
                result[index] = left[i++];
            }
            // 此时在排序先后
            else if (left[i] > right[j]) {
                result[index] = right[j++];
            } else {
                result[index] = left[i++];
            }
        }
        return result;
    }


}